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• StreamReader returning another char

  - by Fernando

  I'm trying to read the content of a file with a StreamReader, that receives a FileStream. The file has some spaces inside (char 32) and the StreamReader is reading them as 0 (char 48). The screenshot shows the FileStream buffer and the StreamReader buffer. Both have the value 32, but when I call Read(), it returns 48. Am I missing something here? By the way, the code is running under .NET Compact Framework. The code that reads the data: public void Read() { using (StreamReader reader = new StreamReader(InputStream, Encoding.ASCII)) { foreach (var property in DataObject.EnumerateProperties()) { OffsetInfo offset = property.GetTextOffset(); reader.BaseStream.Position = offset.Start - 1; StringBuilder builder = new StringBuilder(offset.Size); int count = 0; while (reader.Peek() >= 0 && count < offset.Size) { char c = (char)reader.Read(); if ((int)c != 32 && c != '\r' && c != '\n') { builder.Append(c); count++; } else { reader.BaseStream.Position++; } } property.SetValue(DataObject, Convert.ChangeType(builder.ToString(), property.PropertyType, CultureInfo.CurrentCulture), null ); } } }

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• The use of getters and setters for different programming languages [closed]

  - by leonhart88

  So I know there are a lot of questions on getters and setters in general, but I couldn't find something exactly like my question. I was wondering if people change the use of get/set depending on different languages. I started learning with C++ and was taught to use getters and setters. This is what I understand: In C++ (and Java?), a variable can either be public or private, but we cannot have a mix. For example, I can't have a read-only variable that can still be changed inside the class. It's either all public (can read and change it), or all private (can't read and can only change inside the class). Because of this (and possibly other reasons), we use getters and setters. In MATLAB, I can control the "setaccess" and "getaccess" properties of variables, so that I can make things read-only (can directly access the property, but can't overwrite it). In this case, I don't feel like I need a getter because I can just do class.property. Also, in Python it is considered "Pythonic" to not use getters/setters and to only put things into properties if needed. I don't really understand why its OK to have all public variables in Python, because that's opposite of what I learned when I started with C++. I'm just curious what other people's thoughts are on this. Would you use getters and setters for all languages? Would you only use it for C++/Java and do direct access in MATLAB and Python (which is what I am currently doing)? Is the second option considered bad? For my purposes, I am only referring to simple getters and setters (just return/set the value and do not do anything else). Thanks!

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• Garbage data from serial port.

  - by sasayins

  Hi I wrote a code in Linux platform that read the data in serial port, my code below: int fd; char *rbuff=NULL; struct termios new_opt, old_opt; int ret; fd = open("/dev/ttyS0", O_RDWR | O_NOCTTY); if( fd == -1 ) { printf("Can't open file: %s\n", strerror(errno)); return -1; } tcgetattr(fd, &old_opt); new_opt.c_cflag = B115200 | CS8 | CLOCAL | CREAD; new_opt.c_iflag = IGNPAR /*| ICRNL*/; new_opt.c_oflag = 0; new_opt.c_lflag = ICANON; tcsetattr(fd, TCSANOW, &new_opt); rbuff = malloc(NBUFF); printf("reading..\n"); memset(rbuff,0x00,NBUFF); ret = read(fd, rbuff, NBUFF); printf("value:%s",rbuff); if(ret == -1) { printf("Read error:%s\n",strerror(errno)); return -1; } tcsetattr(fd, TCSANOW, &old_opt); close(fd); My problem is the code above doesn't read the first data that was transmitted, then the second transmission the data is garbage, then the third is the normal data. Did I missed a setting in the serial port? Thanks.

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• Why can't I open a JBoss vfs:/ URL?

  - by skiphoppy

  We are upgrading our application from JBoss 4 to JBoss 6. A couple of pieces of our application get delivered to the client in an unusual way: jars are looked up inside of our application and sent to the client from a servlet, where the client extracts them in order to run certain support functions. In JBoss 4 we would look these jars up with the classloader and find a jar:// URL which would be used to read the jar and send its contents to the client. In JBoss 6 when we perform the lookup we get a vfs:/ URL. I understand that this is from the org.jboss.vfs package. Unfortunately when I call openStream() on this URL and read from the stream, I immediately get an EOF (read() returns -1). What gives? Why can't I read the resource this URL refers to? I've tried trying to access the underlying VFS packages to open the file through the JBoss VFS API, but most of the API appears to be private, and I couldn't find a routine to translate from a vfs:/ URL to a VFS VirtualFile object, so I couldn't get anywhere. I can try to find the file on disk within JBoss, but that approach sounds very failure prone on upgrade. Our old approach was to use Java Web Start to distribute the jars to the client and then look them up within Java Web Start's cache to extract them. But that broke on every minor upgrade of Java because the layout of the cache changed.

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• Reading the .vcproj file with C#

  - by Dulantha Fernando

  We create the vcproj file with the makefileproj keyword so we can use our own build in VS. My question is, using C#, how do you read the "C++" from the following vcproj file: <?xml version="1.0" encoding="Windows-1252"?> <VisualStudioProject ProjectType="Visual C++" Version="8.00" Name="TestCSProj" ProjectGUID="{840501C9-6AFE-8CD6-1146-84208624C0B0}" RootNamespace="TestCSProj" Keyword="MakeFileProj" > <Platforms> <Platform Name="x64" /> <Platform Name="C++" ===> I need to read "C++" /> </Platforms> I used XmlNode and got upto the second Platform: String path = "C:\\blah\\TestCSProj\\TestCSProj\\TestCSProj.vcproj"; FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite); XmlDocument xmldoc = new XmlDocument(); xmldoc.Load(fs); XmlNodeList oldFiles = xmldoc.GetElementsByTagName("Platform"); XmlAttribute name = oldFiles[1].Attributes[0]; Console.WriteLine(name.Name); This will print Name, but I need "C++". How do I read that? Thank you very much in advance

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• ExecuteNonQuery: Connection property has not been initialized

  - by 20151012

  I get an error in my code: The error point at dbcom.ExecuteNonQuery();. Code(connection) public admin_addemp() { InitializeComponent(); con = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\EMPS.accdb;Persist Security Info=True"); con.Open(); ds.Tables.Add(dt); ds.Tables.Add(dt2); } Code (Save button) private void save_btn_Click(object sender, EventArgs e) { OleDbCommand check = new OleDbCommand(); check.Connection = con; check.CommandText = "SELECT COUNT(*) FROM employeeDB WHERE ([EmployeeName]=?)"; check.Parameters.AddWithValue("@EmployeeName", tb_name.Text); if (Convert.ToInt32(check.ExecuteScalar()) == 0) { dbcom2 = new OleDbCommand("SELECT EmployeeID FROM employeeDB WHERE EmployeeID='" + tb_id.Text + "'", con); OleDbParameter param = new OleDbParameter(); param.ParameterName = tb_id.Text; dbcom.Parameters.Add(param); OleDbDataReader read = dbcom2.ExecuteReader(); if (read.HasRows) { MessageBox.Show("The Employee ID '" + tb_id.Text + "' already exist. Please choose another Employee ID."); read.Dispose(); read.Close(); } else { string q = "INSERT INTO employeeDB (EmployeeID, EmployeeName, IC, Address, State, " + " Postcode, DateHired, Phone, ManagerName) VALUES ('" + tb_id.Text + "', " + " '" + tb_name.Text + "', '" + tb_ic.Text + "', '" + tb_add1.Text + "', '" + cb_state.Text + "', " + " '" + tb_postcode.Text + "', '" + dateTimePicker1.Value + "', '" + tb_hp.Text + "', '" + cb_manager.Text + "')"; dbcom = new OleDbCommand(q, con); dbcom.ExecuteNonQuery(); MessageBox.Show("New Employee '" + tb_name.Text + "'- Successfuly Added."); } } else { MessageBox.Show("Employee name '" + tb_name.Text + "' already added into the database"); } ds.Dispose(); } I'm using Microsoft Access 2010 as my database and this is stand alone system. Please help me.

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• suppress error using fread()

  - by Mikey1980

  I wrote a script for screen pops from our soft phone that locates a directory listing for the caller but occasionally they get "Can't read input stream" and the rest of the script quits. Does anyone have any suggestions on how to suppress error the error message and allow the rest of the script to run? Thanks! $i=0; $open = fopen("http://www.411.ca/whitepages/?n=".$_GET['phone'], "r"); $read = fread($open, 9024); fclose($open); eregi("'/(.*)';",$read,$got); $tv = ereg_replace('[[:blank:]]',' ',$got[1]); $url = "http://www.411.ca/".$tv; while ($name=="unknown" && $i < 15) { ## try 15 times before giving up $file = @ fopen($fn=$url,"r") or die ("Can't read input stream"); $text = fread($file,16384); if (preg_match('/"name">(.*?)<\/div>/is',$text,$found)) { $name = $found[1]; } if (preg_match('/"phone">(.*?)<\/div>/is',$text,$found)) { $phone = $found[1]; } if (preg_match('/"address">(.*?)<\/div>/is',$text,$found)) { $address = $found[1]; } fclose($file); $i++; }

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• Reading XML or objects from a Web service

  - by Shawn

  This is my first time working with webservices and I am a bit lost. I successfully called the functions, but I only can get one value from the service. I read that the easiest way is to read xml or create objects and then call their values. Currently I use functions that return the desired value but I need to call them 3 times to get all the data witch is a waste of time and resources. I tried to call the service with the URL and use it as a website or getting the service to work the same way without importing into the program. The thing is that i cant find a way to pass the values into the url, because of that i get only blank pages. What is the fastest way to get my data from the services? I need city name, temperature and a flag if the city is valid. I need to pass the zip code to the service. Thank you. My current code wetther.Weather wether = new wetther.Weather(); string farenhait = wether.GetCityWeatherByZIP(zip).Temperature; string city = wether.GetCityWeatherByZIP(zip).City; bool correct = wether.GetCityWeatherByZIP(zip).Success; I tried it that way // Retrieve XML document XmlTextReader reader = new XmlTextReader("http://xml.weather.yahoo.com/forecastrss?p=94704"); // Skip non-significant whitespace reader.WhitespaceHandling = WhitespaceHandling.Significant; // Read nodes one at a time while (reader.Read()) { // Print out info on node Console.WriteLine("{0}: {1}", reader.NodeType.ToString(), reader.Name); } This one works for the yahoo page but not for mine. I need to use this webservice - http://wsf.cdyne.com/WeatherWS/Weather.asmx

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• VB.NET Update Access Database with DataTable

  - by sinDizzy

  I've been perusing some hep forums and some help books but cant seem to get my head wrapped around this. My task is to read data from two text files and then load that data into an existing MS Access 2007 database. So here is what i'm trying to do: Read data from first text file and for every line of data add data to a DataTable using CarID as my unique field. Read data from second text file and look for existing CarID in DataTable if exists update that row. If it doesnt exist add a new row. once im done push the contents of the DataTable to the database. What i have so far: Dim sSQL As String = "SELECT * FROM tblCars" Dim da As New OleDb.OleDbDataAdapter(sSQL, conn) Dim ds As New DataSet da.Fill(ds, "CarData") Dim cb As New OleDb.OleDbCommandBuilder(da) 'loop read a line of text and parse it out. gets dd, dc, and carId 'create a new empty row Dim dsNewRow As DataRow = ds.Tables("CarData").NewRow() 'update the new row with fresh data dsNewRow.Item("DriveDate") = dd dsNewRow.Item("DCode") = dc dsNewRow.Item("CarNum") = carID 'about 15 more fields 'add the filled row to the DataSet table ds.Tables("CarData").Rows.Add(dsNewRow) 'end loop 'update the database with the new rows da.Update(ds, "CarData") Questions: In constructing my table i use "SELECT * FROM tblCars" but what if that table has millions of records already. Is that not a waste of resources? Should i be trying something different if i want to update with new records? Once Im done with the first text file i then go to my next text file. Whats the best approach here: To First look for an existing record based on CarNum or to create a second table and then merge the two at the end? Finally when the DataTable is done being populated and im pushing it to the database i want to make sure that if records already exist with three primary fields (DriveDate, DCode, and CarNum) that they get updated with new fields and if it doesn't exist then those records get appended. Is that possible with my process? tia AGP

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• C++, Ifstream opens local file but not file on HTTP Server

  - by fammi

  Hi, I am using ifstream to open a file and then read from it. My program works fine when i give location of the local file on my system. for eg /root/Desktop/abc.xxx works fine But once the location is on the http server the file fails to open. for eg http://192.168.0.10/abc.xxx fails to open. Is there any alternate for ifstream when using a URL address? thanks. part of the code where having problem: bool readTillEof = (endIndex == -1) ? true : false; // Open the file in binary mode and seek to the end to determine file size ifstream file ( fileName.c_str ( ), ios::in|ios::ate|ios::binary ); if ( file.is_open ( ) ) { long size = (long) file.tellg ( ); long numBytesRead; if ( readTillEof ) { numBytesRead = size - startIndex; } else { numBytesRead = endIndex - startIndex + 1; } // Allocate a new buffer ptr to read in the file data BufferSptr buf (new Buffer ( numBytesRead ) ); mpStreamingClientEngine->SetResponseBuffer ( nextRequest, buf ); // Seek to the start index of the byte range // and read the data file.seekg ( startIndex, ios::beg ); file.read ( (char *)buf->GetData(), numBytesRead ); // Pass on the data to the SCE // and signal completion of request mpStreamingClientEngine->HandleDataReceived( nextRequest, numBytesRead); mpStreamingClientEngine->MarkRequestCompleted( nextRequest ); // Close the file file.close ( ); } else { // Report error to the Streaming Client Engine // as unable to open file AHS_ERROR ( ConnectionManager, " Error while opening file \"%s\"\n", fileName.c_str ( ) ); mpStreamingClientEngine->HandleRequestFailed( nextRequest, CONNECTION_FAILED ); } }

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• Reading input files in FORTRAN

  - by lollygagger

  Purpose: Create a program that takes two separate files, opens and reads them, assigns their contents to arrays, do some math with those arrays, create a new array with product numbers, print to a new file. Simple enough right? My input files have comment characters at the beginning. One trouble is, they are '#' which are comment characters for most plotting programs, but not FORTRAN. What is a simple way to tell the computer not to look at these characters? Since I have no previous FORTRAN experience, I am plowing through this with two test files. Here is what I have so far: PROGRAM gain IMPLICIT NONE REAL, DIMENSION (1:4, 1:8) :: X, Y, Z OPEN(1, FILE='test.out', & STATUS='OLD', ACTION='READ') ! opens the first file READ(1,*), X OPEN(2, FILE='test2.out', & STATUS='OLD', ACTION='READ') ! opens the second file READ(2,*), Y PRINT*, X, Y Z = X*Y ! PRINT*, Z OPEN(3, FILE='test3.out', STATUS='NEW', ACTION='WRITE') !creates a new file WRITE(3,*), Z CLOSE(1) CLOSE(2) CLOSE(3) END PROGRAM PS. Please do not overwhelm me with a bunch of code monkey gobblety gook. I am a total programming novice. I do not understand all the lingo, that is why I came here instead of searching for help in existing websites. Thanks.

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• How can I write a function template for all types with a particular type trait?

  - by TC

  Consider the following example: struct Scanner { template <typename T> T get(); }; template <> string Scanner::get() { return string("string"); } template <> int Scanner::get() { return 10; } int main() { Scanner scanner; string s = scanner.get<string>(); int i = scanner.get<int>(); } The Scanner class is used to extract tokens from some source. The above code works fine, but fails when I try to get other integral types like a char or an unsigned int. The code to read these types is exactly the same as the code to read an int. I could just duplicate the code for all other integral types I'd like to read, but I'd rather define one function template for all integral types. I've tried the following: struct Scanner { template <typename T> typename enable_if<boost::is_integral<T>, T>::type get(); }; Which works like a charm, but I am unsure how to get Scanner::get<string>() to function again. So, how can I write code so that I can do scanner.get<string>() and scanner.get<any integral type>() and have a single definition to read all integral types? Update: bonus question: What if I want to accept more than one range of classes based on some traits? For example: how should I approach this problem if I want to have three get functions that accept (i) integral types (ii) floating point types (iii) strings, respectively.

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• Fill lower matrix with vector by row, not column

  - by mhermans

  I am trying to read in a variance-covariance matrix written out by LISREL in the following format in a plain text, whitespace separated file: 0.23675E+01 0.86752E+00 0.28675E+01 -0.36190E+00 -0.36190E+00 0.25381E+01 -0.32571E+00 -0.32571E+00 0.84425E+00 0.25598E+01 -0.37680E+00 -0.37680E+00 0.53136E+00 0.47822E+00 0.21120E+01 -0.37680E+00 -0.37680E+00 0.53136E+00 0.47822E+00 0.91200E+00 0.21120E+01 This is actually a lower diagonal matrix (including diagonal): 0.23675E+01 0.86752E+00 0.28675E+01 -0.36190E+00 -0.36190E+00 0.25381E+01 -0.32571E+00 -0.32571E+00 0.84425E+00 0.25598E+01 -0.37680E+00 -0.37680E+00 0.53136E+00 0.47822E+00 0.21120E+01 -0.37680E+00 -0.37680E+00 0.53136E+00 0.47822E+00 0.91200E+00 0.21120E+01 I can read in the values correctly with scan() or read.table(fill=T). I am however not able to correctly store the read-in vector in a matrix. The following code S <- diag(6) S[lower.tri(S,diag=T)] <- d fills the lower matrix by column, while it should fill it by row. Using matrix() does allow for the option byrow=TRUE, but this will fill in the whole matrix, not just the lower half (with diagonal). Is it possible to have both: only fill the lower matrix (with diagonal) and do it by row? (separate issue I'm having: LISREL uses 'D+01' while R only recognises 'E+01' for scientific notation. Can you change this in R to accept also 'D'?)

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• Question about how AppFabric's cache feature can be used.

  - by Kevin Buchan

  Question about how AppFabric's cache feature can be used. I apologize for asking a question that I should be able to answer from the documentation, but I have read and read and searched and cannot answer this question, which leads me to believe that I have a fundamentally flawed understanding of what AppFabric's caching capabilities are intended for. I work for a geographically disperse company. We have a particular application that was originally written as a client/server application. It’s so massive and business critical that we want to baby step converting it to a better architected solution. One of the ideas we had was to convert the app to read its data using WCF calls to a co-located web server that would cache communication with the database in the United States. The nature of the application is such that everyone will tend to be viewing the same 2000 records or so with only occasional updates and those updates will be made by a limited set of users. I was hoping that AppFabric’s cache mechanism would allow me to set up one global cache and when a user in Asia, for example, requested data that was not in the cache or was stale that the web server would read from the database in the USA, provide the data to the user, then update the cache which would propagate that data to the other web servers so that they would know not to go back to the database themselves. Can AppFabric work this way or should I just have the servers retrieve their own data from the database?

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• reading keyboard input without "consuming" it in x86 assembly

  - by Bob

  Ok so here the deal: I have an assignment regarding DOS and interrupts: I need to write a sort of key-logger function that can be called from C code. what it means is a c program would call an assembly function called startlog that would indicate to start logging the keys pressed until a function called endlog is called. the logging should work like this: write the ascii value of any key pressed without disturbing the C code between startlog and endlog, meaning that if the C code also needs to read the input (let's say by scanf, it would work ok). I managed to write the logger by changing the interrupt vector 9th entry (interrupt for keyboard press) to a function I wrote that writes the values to a file, and it works fine. however the C code does not get the input. Basically what i did is read the key pressed using int 21h, however after reading the ascii value it is "consumed" so I need a way to either simulate the key press again or read the value without "consuming" it so next time a key is read it reads the same key. (I described the code in english because it is long and clumsy assembly code)

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• How to increase my "advanced" knowledge of PHP further? (quickly)

  - by Kerry

  I have been working with PHP for years and gotten a very good grasp of the language, created many advanced and not-so-advanced systems that are working very well. The problem I'm running into is that I only learn when I find a need for something that I haven't learned before. This causes me to look up solutions and other code that handles the problem, and so I will learn about a new function or structure that I hadn't seen before. It is in this way that I have learned many of my better techniques (such as studying classes put out by Amazon, Google or other major companies). The main problem with this is the concept of not being able to learn something if you don't know it exists. For instance, it took me several months of programming to learn about the empty() function, and I simply would check the string length using strlen() to check for empty values. I'm now getting into building bigger and bigger systems, and I've started to read blogs like highscalability.com and been researching MySQL replication and server data for scaling. I know that structure of your code is very important to make full systems work. After reading a recent blog about reddit's structure, it made me question if there is some standard or "accepted systems" out there. I have looked into frameworks (I've used Kohana, which I regretted, but decided that PHP frameworks were not for me) and I prefer my own library of functions rather than having a framework. My current structure is a mix between WordPress, Kohana and my own knowledge. The ways I can see as being potentially beneficial are: Read blogs Read tutorials Work with someone else Read a book What would be the best way(s) to "get to the next level" the level of being a very good system developer?

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• Sending Images over Sockets in C

  - by Takkun

  I'm trying to send an image file through a TCP socket in C, but the image isn't being reassembled correctly on the server side. I was wondering if anyone can point out the mistake? I know that the server is receiving the correct file size and it constructs a file of that size, but it isn't an image file. Client //Get Picture Size printf("Getting Picture Size\n"); FILE *picture; picture = fopen(argv[1], "r"); int size; fseek(picture, 0, SEEK_END); size = ftell(picture); //Send Picture Size printf("Sending Picture Size\n"); write(sock, &size, sizeof(size)); //Send Picture as Byte Array printf("Sending Picture as Byte Array\n"); char send_buffer[size]; while(!feof(picture)) { fread(send_buffer, 1, sizeof(send_buffer), picture); write(sock, send_buffer, sizeof(send_buffer)); bzero(send_buffer, sizeof(send_buffer)); } Server //Read Picture Size printf("Reading Picture Size\n"); int size; read(new_sock, &size, sizeof(1)); //Read Picture Byte Array printf("Reading Picture Byte Array\n"); char p_array[size]; read(new_sock, p_array, size); //Convert it Back into Picture printf("Converting Byte Array to Picture\n"); FILE *image; image = fopen("c1.png", "w"); fwrite(p_array, 1, sizeof(p_array), image); fclose(image);

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• Value is zero after filter SQL in C#

  - by Chuki2

  I`m new in C#.. I have write function to filter department. And this function will return idDepartment. New problem is, department keep value "System.Windows.Forms.Label, Text : ADMIN ", that`s why i got zero. So how can i take "ADMIN" only and keep to department? Update : public partial class frmEditStaff : Form { private string connString; private string userId, department; //Department parameter coming from here private string conString = "Datasource"; public frmEditStaff(string strUserID, string strPosition) { InitializeComponent(); //Pass value from frmListStaff to userID text box tbStaffId.Text = strUserID.ToString(); userId = strUserID.ToString(); department = strPosition.ToString(); } This code below is working, don`t have any problem. public int lookUpDepart() { int idDepart=0; using (SqlConnection openCon = new SqlConnection(conString)) { string lookUpDepartmenId = "SELECT idDepartment FROM tbl_department WHERE department = '" + department + "';"; openCon.Open(); using (SqlCommand querylookUpDepartmenId = new SqlCommand(lookUpDepartmenId, openCon)) { SqlDataReader read = querylookUpDepartmenId.ExecuteReader(); while (read.Read()) { idDepart = int.Parse(read[0].ToString()); break; } } openCon.Close(); return idDepart; } } Thanks for help. Happy nice day!

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• task_current redundant field

  - by user341940

  Hi, I'm writing a kernel module that reads from a /proc file. When someone writes into the /proc file the reader will read it, but if it reads again while there is no "new" write, it should be blocked. In order to remember if we already read, i need to keep a map of the latest buffer that process read. To avoid that, I was told that there might be some redundant field inside the current- (task_struct struct) that i can use to my benefits in order to save some states on the current process. How can I find such fields ? and how can i avoid them being overwritten ? I read somewhere that i can use the offset field inside the struct in order to save my information there and i need to block lseek operations so that field will stay untouched. How can I do so ? and where is that offset field, i can't find it inside the task_Struct. Thanks and I need to save for each process some information in order to map it against other information. I can write a ma

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• Trouble understanding the semantics of volatile in Java

  - by HungryTux

  I've been reading up about the use of volatile variables in Java. I understand that they ensure instant visibility of their latest updates to all the threads running in the system on different cores/processors. However no atomicity of the operations that caused these updates is ensured. I see the following literature being used frequently A write to a volatile field happens-before every read of that same field . This is where I am a little confused. Here's a snippet of code which should help me better explain my query. volatile int x = 0; volatile int y = 0; Thread-0: | Thread-1: | if (x==1) { | if (y==1) { return false; | return false; } else { | } else { y=1; | x=1; return true; | return true; } | } Since x & y are both volatile, we have the following happens-before edges between the write of y in Thread-0 and read of y in Thread-1 between the write of x in Thread-1 and read of x in Thread-0 Does this imply that, at any point of time, only one of the threads can be in its 'else' block(since a write would happen before the read)? It may well be possible that Thread-0 starts, loads x, finds it value as 0 and right before it is about to write y in the else-block, there's a context switch to Thread-1 which loads y finds it value as 0 and thus enters the else-block too. Does volatile guard against such context switches (seems very unlikely)?

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• Best Methods for Dynamically Creating New Objects

  - by frankV

  I'm looking for a method to dynamically create new class objects during runtime of a program. So far what I've read leads me to believe it's not easy and normally reserved for more advanced program requirements. What I've tried so far is this: // create a vector of type class vector<class_name> vect; // and use push_back (method 1) vect.push_back(*new Object); //or use for loop and [] operator (method 2) vect[i] = *new Object; neither of these throw errors from the compiler, but I'm using ifstream to read data from a file and dynamically create the objects... the file read is taking in some weird data and occasionally reading a memory address, and it's obvious to me it's due to my use/misuse of the code snippet above. The file read code is as follows: // in main ifstream fileIn fileIn.open( fileName.c_str() ); // passes to a separate function along w/ vector loadObjects (fileIn, vect); void loadObjects (ifstream& is, vector<class_name>& Object) { int data1, data2, data3; int count = 0; string line; if( is.good() ){ for (int i = 0; i < 4; i++) { is >> data1 >> data2 >> data3; if (data1 == 0) { vect.push_back(*new Object(data2, data3) ) } } } }

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• C# in Depth, Third Edition by Jon Skeet, Manning Publications Co. Book Review

  - by Compudicted

  Originally posted on: http://geekswithblogs.net/Compudicted/archive/2013/10/24/c-in-depth-third-edition-by-jon-skeet-manning-publications.aspx I started reading this ebook on September 28, 2013, the same day it was sent my way by Manning Publications Co. for review while it still being fresh off the press. So 1st thing – thanks to Manning for this opportunity and a free copy of this must have on every C# developer’s desk book! Several hours ago I finished reading this book (well, except a for a large portion of its quite lengthy appendix). I jumped writing this review right away while still being full of emotions and impressions from reading it thoroughly and running code examples. Before I go any further I would like say that I used to program on various platforms using various languages starting with the Mainframe and ending on Windows, and I gradually shifted toward dealing with databases more than anything, however it happened with me to program in C# 1 a lot when it was first released and then some C# 2 with a big leap in between to C# 5. So my perception and experience reading this book may differ from yours. Also what I want to tell is somewhat funny that back then, knowing some Java and seeing C# 1 released, initially made me drawing a parallel that it is a copycat language, how wrong was I… Interestingly, Jon programs in Java full time, but how little it was mentioned in the book! So more on the book: Be informed, this is not a typical “Recipes”, “Cookbook” or any set of ready solutions, it is rather targeting mature, advanced developers who do not only know how to use a number of features, but are willing to understand how the language is operating “under the hood”. I must state immediately, at the same time I am glad the author did not go into the murky depths of the MSIL, so this is a very welcome decision on covering a modern language as C# for me, thank you Jon! Frankly, not all was that rosy regarding the tone and structure of the book, especially the the first half or so filled me with several negative and positive emotions overpowering each other. To expand more on that, some statements in the book appeared to be bias to me, or filled with pre-justice, it started to look like it had some PR-sole in it, but thankfully this was all gone toward the end of the 1st third of the book. Specifically, the mention on the C# language popularity, Java is the #1 language as per https://sites.google.com/site/pydatalog/pypl/PyPL-PopularitY-of-Programming-Language (many other sources put C at the top which I highly doubt), also many interesting functional languages as Clojure and Groovy appeared and gained huge traction which run on top of Java/JVM whereas C# does not enjoy such a situation. If we want to discuss the popularity in general and say how fast a developer can find a new job that pays well it would be indeed the very Java, C++ or PHP, never C#. Or that phrase on language preference as a personal issue? We choose where to work or we are chosen because of a technology used at a given software shop, not vice versa. The book though it technically very accurate with valid code, concise examples, but I wish the author would give more concrete, real-life examples on where each feature should be used, not how. Another point to realize before you get the book is that it is almost a live book which started to be written when even C# 3 wasn’t around so a lot of ground is covered (nearly half of the book) on the pre-C# 3 feature releases so if you already have a solid background in the previous releases and do not plan to upgrade, perhaps half of the book can be skipped, otherwise this book is surely highly recommended. Alas, for me it was a hard read, most of it. It was not boring (well, only may be two times), it was just hard to grasp some concepts, but do not get me wrong, it did made me pause, on several occasions, and made me read and re-read a page or two. At times I even wondered if I have any IQ at all (LOL). Be prepared to read A LOT on generics, not that they are widely used in the field (I happen to work as a consultant and went thru a lot of code at many places) I can tell my impression is the developers today in best case program using examples found at OpenStack.com. Also unlike the Java world where having the most recent version is nearly mandated by the OSS most companies on the Microsoft platform almost never tempted to upgrade the .Net version very soon and very often. As a side note, I was glad to see code recently that included a nullable variable (myvariable? notation) and this made me smile, besides, I recommended that person this book to expand her knowledge. The good things about this book is that Jon maintains an active forum, prepared code snippets and even a small program (Snippy) that is happy to run the sample code saving you from writing any plumbing code. A tad now on the C# language itself – it sure enjoyed a wonderful road toward perfection and a very high adoption, especially for ASP development. But to me all the recent features that made this statically typed language more dynamic look strange. Don’t we have F#? Which supposed to be the dynamic language? Why do we need to have a hybrid language? Now the developers live their lives in dualism of the static and dynamic variables! And LINQ to SQL, it is covered in depth, but wasn’t it supposed to be dropped? Also it seems that very little is being added, and at a slower pace, e.g. Roslyn will come in late 2014 perhaps, and will be probably the only main feature. Again, it is quite hard to read this book as various chapters, C# versions mentioned every so often only if I only could remember what was covered exactly where! So the fact it has so many jumps/links back and forth I recommend the ebook format to make the navigations easier to perform and I do recommend using software that allows bookmarking, also make sure you have access to plenty of coffee and pizza (hey, you probably know this joke – who a programmer is) ! In terms of closing, if you stuck at C# 1 or 2 level, it is time to embrace the power of C# 5! Finally, to compliment Manning, this book unlike from any other publisher so far, was the only one as well readable (put it formatted) on my tablet as in Adobe Reader on a laptop.

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• Psychonauts crashes right after entering load save door

  - by user67974

  Psychonauts crashes right after entering the 'Load Save' door. Here is the terminal output: Shader assembly time: 0.88 seconds Found OpenAL device: 'Simple Directmedia Layer' Found OpenAL device: 'ALSA Software' Found OpenAL device: 'OSS Software' Found OpenAL device: 'PulseAudio Software' Opened OpenAL Device: '(null)' ERROR: CAudioDrv::CAudioDrv->alGenSources reports AL_INVALID_VALUE error. PSYCHONAUTS UNIX FILENAME: corrected 'workresource/sounds/commonfx.isb' to 'WorkResource/Sounds/commonfx.isb' PSYCHONAUTS UNIX FILENAME: corrected 'workresource/sounds/commonvoice.isb' to 'WorkResource/Sounds/commonvoice.isb' PSYCHONAUTS UNIX FILENAME: corrected 'workresource/sounds/commonmusic.isb' to 'WorkResource/Sounds/commonmusic.isb' PSYCHONAUTS UNIX FILENAME: corrected 'workresource/sounds/commonmentalfx.isb' to 'WorkResource/Sounds/commonmentalfx.isb' PSYCHONAUTS UNIX FILENAME: corrected 'workresource/sounds/commonmenfxmem.isb' to 'WorkResource/Sounds/commonmenfxmem.isb' PSYCHONAUTS UNIX FILENAME: corrected 'workresource/sounds/commonfxmem.isb' to 'WorkResource/Sounds/commonfxmem.isb' GameApp::StartUp InitSoundFiles() completed in 0.15 seconds GameApp::StartUp Load some common textures completed in 0.00 seconds WARN: ENGINE: Lua garbage collection starting FreeUnusedBlocksInBuckets released 0 Kb GameApp::StartUp InitEntities() completed in 0.02 seconds PSYCHONAUTS UNIX FILENAME: corrected 'WorkResource/SavedGames/savegameprefs.ini' to 'WorkResource/SAVEDGAMES/savegameprefs.ini' PSYCHONAUTS UNIX FILENAME: corrected 'WorkResource/SavedGames/savegameprefs.ini' to 'WorkResource/SAVEDGAMES/savegameprefs.ini' GameApp::StartUp m_pSaveLoadInterface->Startup() completed in 0.00 seconds GameApp::StartUp m_UserInterface.Setup() completed in 0.00 seconds STUBBED: multisample at EDisplayOptionsWidget (/home/icculus/projects/psychonauts/Source/game/luatest/Game/UIPCDisplayOptions.cpp:97) STUBBED: VK_* at CheckVirtualKey (/home/icculus/projects/psychonauts/Source/CommonLibs/DirectX/SDLInput.cpp:1443) Game: Engine Running hook startup Game: Engine -> SetupGlobalObjects Game: Engine -> SetupLevelMenu Game: Engine -> InitMath GameApp::StartUp InitLua2() completed in 0.00 seconds GameApp::StartUp SetupLevelMenu() completed in 0.00 seconds STUBBED: do we even use this? at InitSocket (/home/icculus/projects/psychonauts/Source/game/luatest/Game/Gameplaylogger.cpp:210) GameApp::StartUp Post-Install total completed in 0.20 seconds Start Up completed in 1.57 seconds UnixMain: StartUp successful.. Working directory: /opt/psychonauts STUBBED: dispatch SDL events at PCMainHandleAnyWindowsMessages (/home/icculus/projects/psychonauts/Source/game/luatest/UnixMain.cpp:56) STUBBED: write me at GetJoystickInput (/home/icculus/projects/psychonauts/Source/CommonLibs/DirectX/SDLInput.cpp:428) STUBBED: write me at GetJoystickActionValue (/home/icculus/projects/psychonauts/Source/CommonLibs/DirectX/SDLInput.cpp:613) PSYCHONAUTS UNIX FILENAME: corrected 'workresource/cutScenes/prerendered/dflogo.bik' to 'WorkResource/cutscenes/prerendered/DFLogo.bik' Prerender subtitle file: workresource\cutScenes\prerendered\dflogo.dfs not found PSYCHONAUTS UNIX FILENAME: corrected 'workresource/cutScenes/prerendered/dflogo.bik' to 'WorkResource/cutscenes/prerendered/DFLogo.bik' STUBBED: fixed function pipeline? at setColorOp (/home/icculus/projects/psychonauts/Source/CommonLibs/DFGraphics/Texture.cpp:2097) STUBBED: fixed function pipeline? at setColorArg1 (/home/icculus/projects/psychonauts/Source/CommonLibs/DFGraphics/Texture.cpp:2106) STUBBED: fixed function pipeline? at setColorArg2 (/home/icculus/projects/psychonauts/Source/CommonLibs/DFGraphics/Texture.cpp:2115) STUBBED: fixed function pipeline? at setAlphaOp (/home/icculus/projects/psychonauts/Source/CommonLibs/DFGraphics/Texture.cpp:2124) STUBBED: fixed function pipeline? at setAlphaArg1 (/home/icculus/projects/psychonauts/Source/CommonLibs/DFGraphics/Texture.cpp:2133) STUBBED: fixed function pipeline? at setAlphaArg2 (/home/icculus/projects/psychonauts/Source/CommonLibs/DFGraphics/Texture.cpp:2142) STUBBED: fixed function pipeline? at setProjected (/home/icculus/projects/psychonauts/Source/CommonLibs/DFGraphics/Texture.cpp:2223) LOC WARN: Could not open Localization file 'Localization/English/_StringTable.lub' STUBBED: memory status at UpdateMemoryTracking (/home/icculus/projects/psychonauts/Source/game/luatest/Game/GameApp.cpp:4884) WARN: Couldn't resize array to 128; out-of-bounds elements are still in use: Vertex Pool, 188 Loading new level 'STMU' STUBBED: Need multithreaded GL at DisplayLoadingScreen (/home/icculus/projects/psychonauts/Source/game/luatest/Game/LoadingScreen.cpp:83) ========================= Memory post unload level ========================= ========================= LOC WARN: Could not open Localization file 'Localization/English/ST_StringTable.lub' DaveD: Info: Texture pack file contains 137 textures Doing a texture readback for locking! Game: Engine Saved[GLOBAL]: InstaHintFord_HostileRecord = [table] Game: Engine Saved[GLOBAL]: InstaHintFord_HostileOrder = [table] WARN: Redundant packfile read: anims\thought_bubble\bubblefirestarting.jan WARN: Redundant packfile read: anims\thought_bubble\bubbleintothemind.jan WARN: Redundant packfile read: anims\thought_bubble\bubbleinvisibility.jan WARN: Redundant packfile read: anims\thought_bubble\bubblepopperfill.jan WARN: Redundant packfile read: anims\thought_bubble\bubbletelekinesis.jan Initializing level script (if there is one) PSYCHONAUTS UNIX FILENAME: corrected 'workresource/sounds/stfx.isb' to 'WorkResource/Sounds/stfx.isb' Game: Engine Reloading goals: Game: Engine Saved[GLOBAL]: NextEncouragement = '/GLZF014TO/ 10' Game: Engine Saved[GLOBAL]: bUsedSalts = 0 Game: Engine Saved[GLOBAL]: bSTEntered = 1 Game: Engine Saved[GLOBAL]: memoriesST = 1 Game: Engine Saved[GLOBAL]: PsiBallColor = 'red' Game: Engine Saved[ST]: lastSubLevel = 'STMU' Game: Engine LOADING LEVEL st.STMU Game: Engine Saved[CA]: CALevelState = 1 Game: Engine Cutscene progression: CS Script moving from state nil to state nil, resultant state nil. Time: 0.124746672809124. * Stack Trace 1: (null) (line -1, file '(none)) () 2: SpawnScript (line -1, file 'C) (global) 3: onBeginLevel (line -1, file '(none)) (field) 4: (null) (line -1, file '(none)) () WARN: Cannot call GetDirectoryListing when running from the DVD Game: Engine Raz spawning at DartStart startpoint VM : LevelScript could not find script 'doorrimlight1' * Stack Trace 1: (null) (line -1, file '(none)) () WARN: (none(-1) SetEntityAlpha LevelScript: NULL script object passed Game: Engine Saved[GLOBAL]: bLoadedFromMainMenu = 1 Game: Engine Saved[GLOBAL]: NextEncouragement = '/GLZF014TO/ 10' Game: Engine Saved[GLOBAL]: NeedRankIncrement = 0 STUBBED: Need multithreaded GL at HideLoadingScreen (/home/icculus/projects/psychonauts/Source/game/luatest/Game/LoadingScreen.cpp:110) WARN: ENGINE: Lua garbage collection starting FreeUnusedBlocksInBuckets released 0 Kb Game: Engine Saved[GLOBAL]: SplineFigmentTVSizex = 4.51434326171875 Game: Engine Saved[GLOBAL]: SplineFigmentTVSizey = 46.38104248046875 Game: Engine Saved[GLOBAL]: SplineFigmentTVSizez = 47.08810424804688 WARN: (none(-1) SetNewAction LevelScript: no string passed ====================== Asset load progression ====================== Initial: 2.518 MB Vertex, 8.688 MB Texture Level : 3.719 MB Vertex, 22.535 MB Texture Scripts: 3.747 MB Vertex, 22.848 MB Texture ====================== ====================== Memory post level load ====================== ====================== WARN: ENGINE: Lua garbage collection starting FreeUnusedBlocksInBuckets released 0 Kb DaveD: Level loaded in 0.14 seconds Anim: anims\objects\tk_arrow_idle.jan: loaded (1 frames latency) Anim: anims\dartnew\helmet\darthelmetdn.jan: loaded (1 frames latency) Anim: anims\thought_bubble\shieldloop.jan: loaded (1 frames latency) Anim: anims\dartnew\standready.jan: loaded (1 frames latency) Anim: anims\dartnew\walkmove.jan: loaded (1 frames latency) Anim: anims\janitor\hint_end.jan: loaded (1 frames latency) Anim: anims\thought_bubble\ballstatic.jan: loaded (1 frames latency) Anim: anims\dartnew\actionfall.jan: loaded (1 frames latency) Anim: anims\dartnew\standstill.jan: loaded (1 frames latency) Anim: anims\dartnew\pack\packbounce_lf_rt.jan: loaded (1 frames latency) Anim: anims\dartnew\pack\packbounce_up_dn.jan: loaded (1 frames latency) Anim: anims\dartnew\helmet\darthelmetdefpose.jan: loaded (1 frames latency) 1: 1 (number) 1: 1 (number) STUBBED: This is probably wrong at GetDt (/home/icculus/projects/psychonauts/Source/CommonLibs/DFUtil/Profiler.cpp:181) STUBBED: set specular highlights at setSpecularEnable (/home/icculus/projects/psychonauts/Source/CommonLibs/DFGraphics/Renderer.cpp:2035) Anim: anims\dartnew\trnrtcycle.jan: loaded (1 frames latency) Anim: anims\dartnew\run.jan: loaded (1 frames latency) Anim: anims\dartnew\walk.jan: loaded (1 frames latency) Anim: anims\thought_bubble\bubbledoublejump.jan: loaded (1 frames latency) Anim: anims\dartnew\longjump.jan: loaded (1 frames latency) Anim: anims\menubrain\door1crack.jan: loaded (1 frames latency) Anim: anims\menubrain\door1crackedidle.jan: loaded (1 frames latency) Anim: anims\menubrain\door1closedidle.jan: loaded (1 frames latency) Anim: anims\dartnew\180.jan: loaded (1 frames latency) Anim: anims\menubrain\door3crack.jan: loaded (1 frames latency) Anim: anims\menubrain\door3crackedidle.jan: loaded (1 frames latency) Anim: anims\menubrain\door3closedidle.jan: loaded (1 frames latency) Anim: anims\dartnew\railslide45angle.jan: loaded (1 frames latency) Anim: anims\dartnew\railslideflat.jan: loaded (1 frames latency) Anim: anims\dartnew\trnlfcycle.jan: loaded (1 frames latency) WARN: (none(-1) SetNewAction LevelScript: no string passed Anim: anims\dartnew\mainmenu_jump.jan: loaded (1 frames latency) Anim: anims\menubrain\door1open.jan: loaded (1 frames latency) ERROR: Assert in /home/icculus/projects/psychonauts/Source/game/luatest/../../CommonLibs/Include/../DFGraphics/Color.h, line 96 v.x >= 0.0f && v.x <= 1.0f && v.y >= 0.0f && v.y <= 1.0f && v.z >= 0.0f && v.z <= 1.0f && v.w >= 0.0f && v.w <= 1.0f Encountered Error: Psychonauts has encountered an error /home/icculus/projects/psychonauts/Source/game/luatest/../../CommonLibs/Include/../DFGraphics/Color.h, line 96 v.x >= 0.0f && v.x <= 1.0f && v.y >= 0.0f && v.y <= 1.0f && v.z >= 0.0f && v.z <= 1.0f && v.w >= 0.0f && v.w <= 1.0f Please contact technical support at http://www.doublefine.com. I am currently using Bumblebee for hybrid graphics, if that helps in any way.

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• how to use serial port in UDK using windows DLL and DLLBind directive?

  - by Shayan Abbas

  I want to use serial port in UDK, For that purpose i use a windows DLL and DLLBind directive. I have a thread in windows DLL for serial port data recieve event. My problem is: this thread doesn't work properly. Please Help me. below is my code SerialPortDLL Code: // SerialPortDLL.cpp : Defines the exported functions for the DLL application. // #include "stdafx.h" #include "Cport.h" extern "C" { // This is an example of an exported variable //SERIALPORTDLL_API int nSerialPortDLL=0; // This is an example of an exported function. //SERIALPORTDLL_API int fnSerialPortDLL(void) //{ // return 42; //} CPort *sp; __declspec(dllexport) void Open(wchar_t* portName) { sp = new CPort(portName); //MessageBox(0,L"ha ha!!!",L"ha ha",0); //MessageBox(0,portName,L"ha ha",0); } __declspec(dllexport) void Close() { sp->Close(); MessageBox(0,L"ha ha!!!",L"ha ha",0); } __declspec(dllexport) wchar_t *GetData() { return sp->GetData(); } __declspec(dllexport) unsigned int GetDSR() { return sp->getDSR(); } __declspec(dllexport) unsigned int GetCTS() { return sp->getCTS(); } __declspec(dllexport) unsigned int GetRing() { return sp->getRing(); } } CPort class code: #include "stdafx.h" #include "CPort.h" #include "Serial.h" CSerial serial; HANDLE HandleOfThread; LONG lLastError = ERROR_SUCCESS; bool fContinue = true; HANDLE hevtOverlapped; HANDLE hevtStop; OVERLAPPED ov = {0}; //char szBuffer[101] = ""; wchar_t *szBuffer = L""; wchar_t *data = L""; DWORD WINAPI ThreadHandler( LPVOID lpParam ) { // Keep reading data, until an EOF (CTRL-Z) has been received do { MessageBox(0,L"ga ga!!!",L"ga ga",0); //Sleep(10); // Wait for an event lLastError = serial.WaitEvent(&ov); if (lLastError != ERROR_SUCCESS) { //LOG( " Unable to wait for a COM-port event" ); } // Setup array of handles in which we are interested HANDLE ahWait[2]; ahWait[0] = hevtOverlapped; ahWait[1] = hevtStop; // Wait until something happens switch (::WaitForMultipleObjects(sizeof(ahWait)/sizeof(*ahWait),ahWait,FALSE,INFINITE)) { case WAIT_OBJECT_0: { // Save event const CSerial::EEvent eEvent = serial.GetEventType(); // Handle break event if (eEvent & CSerial::EEventBreak) { //LOG( " ### BREAK received ###" ); } // Handle CTS event if (eEvent & CSerial::EEventCTS) { //LOG( " ### Clear to send %s ###", serial.GetCTS() ? "on":"off" ); } // Handle DSR event if (eEvent & CSerial::EEventDSR) { //LOG( " ### Data set ready %s ###", serial.GetDSR() ? "on":"off" ); } // Handle error event if (eEvent & CSerial::EEventError) { switch (serial.GetError()) { case CSerial::EErrorBreak: /*LOG( " Break condition" );*/ break; case CSerial::EErrorFrame: /*LOG( " Framing error" );*/ break; case CSerial::EErrorIOE: /*LOG( " IO device error" );*/ break; case CSerial::EErrorMode: /*LOG( " Unsupported mode" );*/ break; case CSerial::EErrorOverrun: /*LOG( " Buffer overrun" );*/ break; case CSerial::EErrorRxOver: /*LOG( " Input buffer overflow" );*/ break; case CSerial::EErrorParity: /*LOG( " Input parity error" );*/ break; case CSerial::EErrorTxFull: /*LOG( " Output buffer full" );*/ break; default: /*LOG( " Unknown" );*/ break; } } // Handle ring event if (eEvent & CSerial::EEventRing) { //LOG( " ### RING ###" ); } // Handle RLSD/CD event if (eEvent & CSerial::EEventRLSD) { //LOG( " ### RLSD/CD %s ###", serial.GetRLSD() ? "on" : "off" ); } // Handle data receive event if (eEvent & CSerial::EEventRecv) { // Read data, until there is nothing left DWORD dwBytesRead = 0; do { // Read data from the COM-port lLastError = serial.Read(szBuffer,33,&dwBytesRead); if (lLastError != ERROR_SUCCESS) { //LOG( "Unable to read from COM-port" ); } if( dwBytesRead == 33 && szBuffer[0]=='$' ) { // Finalize the data, so it is a valid string szBuffer[dwBytesRead] = '\0'; ////LOG( "\n%s\n", szBuffer ); data = szBuffer; } } while (dwBytesRead > 0); } } break; case WAIT_OBJECT_0+1: { // Set the continue bit to false, so we'll exit fContinue = false; } break; default: { // Something went wrong //LOG( "Error while calling WaitForMultipleObjects" ); } break; } } while (fContinue); MessageBox(0,L"kka kk!!!",L"kka ga",0); return 0; } CPort::CPort(wchar_t *portName) { // Attempt to open the serial port (COM2) //lLastError = serial.Open(_T(portName),0,0,true); lLastError = serial.Open(portName,0,0,true); if (lLastError != ERROR_SUCCESS) { //LOG( "Unable to open COM-port" ); } // Setup the serial port (115200,8N1, which is the default setting) lLastError = serial.Setup(CSerial::EBaud115200,CSerial::EData8,CSerial::EParNone,CSerial::EStop1); if (lLastError != ERROR_SUCCESS) { //LOG( "Unable to set COM-port setting" ); } // Register only for the receive event lLastError = serial.SetMask(CSerial::EEventBreak | CSerial::EEventCTS | CSerial::EEventDSR | CSerial::EEventError | CSerial::EEventRing | CSerial::EEventRLSD | CSerial::EEventRecv); if (lLastError != ERROR_SUCCESS) { //LOG( "Unable to set COM-port event mask" ); } // Use 'non-blocking' reads, because we don't know how many bytes // will be received. This is normally the most convenient mode // (and also the default mode for reading data). lLastError = serial.SetupReadTimeouts(CSerial::EReadTimeoutNonblocking); if (lLastError != ERROR_SUCCESS) { //LOG( "Unable to set COM-port read timeout" ); } // Create a handle for the overlapped operations hevtOverlapped = ::CreateEvent(0,TRUE,FALSE,0);; if (hevtOverlapped == 0) { //LOG( "Unable to create manual-reset event for overlapped I/O" ); } // Setup the overlapped structure ov.hEvent = hevtOverlapped; // Open the "STOP" handle hevtStop = ::CreateEvent(0,TRUE,FALSE,_T("Overlapped_Stop_Event")); if (hevtStop == 0) { //LOG( "Unable to create manual-reset event for stop event" ); } HandleOfThread = CreateThread( NULL, 0, ThreadHandler, 0, 0, NULL); } CPort::~CPort() { //fContinue = false; //CloseHandle( HandleOfThread ); //serial.Close(); } void CPort::Close() { fContinue = false; CloseHandle( HandleOfThread ); serial.Close(); } wchar_t *CPort::GetData() { return data; } bool CPort::getCTS() { return serial.GetCTS(); } bool CPort::getDSR() { return serial.GetDSR(); } bool CPort::getRing() { return serial.GetRing(); } Unreal Script Code: class MyPlayerController extends GamePlayerController DLLBind(SerialPortDLL); dllimport final function Open(string portName); dllimport final function Close(); dllimport final function string GetData();

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• SQL Server Table Polling by Multiple Subscribers

  - by Daniel Hester

  Background Designing Stored Procedures that are safe for multiple subscribers (to call simultaneously) can be challenging.  For example let’s say that you want multiple worker processes to poll a shared work queue that’s encapsulated as a SQL Table. This is a common scenario and through experience you’ll find that you want to use Table Hints to prevent unwanted locking when performing simultaneous queries on the same table. There are three table hints to consider: NOLOCK, READPAST and UPDLOCK. Both NOLOCK and READPAST table hints allow you to SELECT from a table without placing a LOCK on that table. However, SELECTs with the READPAST hint will ignore any records that are locked due to being updated/inserted (or otherwise “dirty”), whereas a SELECT with NOLOCK ignores all locks including dirty reads. For the initial update of the flag (that marks the record as available for subscription) I don’t use the NOLOCK Table Hint because I want to be sensitive to the “active” records in the table and I want to exclude them.  I use an Update Lock (UPDLOCK) in conjunction with a WHERE clause that uses a sub-select with a READPAST Table Hint in order to explicitly lock the records I’m updating (UPDLOCK) but not place a lock on the table when selecting the records that I’m going to update (READPAST). UPDATES should be allowed to lock the rows affected because we’re probably changing a flag on a record so that it is not included in a SELECT from another subscriber. On the UPDATE statement we should explicitly use the UPDLOCK to guard against lock escalation. A SELECT to check for the next record(s) to process can result in a shared read lock being held by more than one subscriber polling the shared work queue (SQL table). It is expected that more than one worker process (or server) might try to process the same new record(s) at the same time. When each process then tries to obtain the update lock, none of them can because another process has a shared read lock in place. Thus without the UPDLOCK hint the result would be a lock escalation deadlock; however with the UPDLOCK hint this condition is mitigated against. Note that using the READPAST table hint requires that you also set the ISOLATION LEVEL of the transaction to be READ COMMITTED (rather than the default of SERIALIZABLE). Guidance In the Stored Procedure that returns records to the multiple subscribers: Perform the UPDATE first. Change the flag that makes the record available to subscribers.  Additionally, you may want to update a LastUpdated datetime field in order to be able to check for records that “got stuck” in an intermediate state or for other auditing purposes. In the UPDATE statement use the (UPDLOCK) Table Hint on the UPDATE statement to prevent lock escalation. In the UPDATE statement also use a WHERE Clause that uses a sub-select with a (READPAST) Table Hint to select the records that you’re going to update. In the UPDATE statement use the OUTPUT clause in conjunction with a Temporary Table to isolate the record(s) that you’ve just updated and intend to return to the subscriber. This is the fastest way to update the record(s) and to get the records’ identifiers within the same operation. Finally do a set-based SELECT on the main Table (using the Temporary Table to identify the records in the set) with either a READPAST or NOLOCK table hint.  Use NOLOCK if there are other processes (besides the multiple subscribers) that might be changing the data that you want to return to the multiple subscribers; or use READPAST if you're sure there are no other processes (besides the multiple subscribers) that might be updating column data in the table for other purposes (e.g. changes to a person’s last name).  NOLOCK is generally the better fit in this part of the scenario. See the following as an example: CREATE PROCEDURE [dbo].[usp_NewCustomersSelect] AS BEGIN -- OVERRIDE THE DEFAULT ISOLATION LEVEL SET TRANSACTION ISOLATION LEVEL READ COMMITTED -- SET NOCOUNT ON SET NOCOUNT ON -- DECLARE TEMP TABLE -- Note that this example uses CustomerId as an identifier; -- you could just use the Identity column Id if that’s all you need. DECLARE @CustomersTempTable TABLE ( CustomerId NVARCHAR(255) ) -- PERFORM UPDATE FIRST -- [Customers] is the name of the table -- [Id] is the Identity Column on the table -- [CustomerId] is the business document key used to identify the -- record globally, i.e. in other systems or across SQL tables -- [Status] is INT or BIT field (if the status is a binary state) -- [LastUpdated] is a datetime field used to record the time of the -- last update UPDATE [Customers] WITH (UPDLOCK) SET [Status] = 1, [LastUpdated] = GETDATE() OUTPUT [INSERTED].[CustomerId] INTO @CustomersTempTable WHERE ([Id] = (SELECT TOP 100 [Id] FROM [Customers] WITH (READPAST) WHERE ([Status] = 0) ORDER BY [Id] ASC)) -- PERFORM SELECT FROM ENTITY TABLE SELECT [C].[CustomerId], [C].[FirstName], [C].[LastName], [C].[Address1], [C].[Address2], [C].[City], [C].[State], [C].[Zip], [C].[ShippingMethod], [C].[Id] FROM [Customers] AS [C] WITH (NOLOCK), @CustomersTempTable AS [TEMP] WHERE ([C].[CustomerId] = [TEMP].[CustomerId]) END In a system that has been designed to have multiple status values for records that need to be processed in the Work Queue it is necessary to have a “Watch Dog” process by which “stale” records in intermediate states (such as “In Progress”) are detected, i.e. a [Status] of 0 = New or Unprocessed; a [Status] of 1 = In Progress; a [Status] of 2 = Processed; etc.. Thus, if you have a business rule that states that the application should only process new records if all of the old records have been processed successfully (or marked as an error), then it will be necessary to build a monitoring process to detect stalled or stale records in the Work Queue, hence the use of the LastUpdated column in the example above. The Status field along with the LastUpdated field can be used as the criteria to detect stalled / stale records. It is possible to put this watchdog logic into the stored procedure above, but I would recommend making it a separate monitoring function. In writing the stored procedure that checks for stale records I would recommend using the same kind of lock semantics as suggested above. The example below looks for records that have been in the “In Progress” state ([Status] = 1) for greater than 60 seconds: CREATE PROCEDURE [dbo].[usp_NewCustomersWatchDog] AS BEGIN -- TO OVERRIDE THE DEFAULT ISOLATION LEVEL SET TRANSACTION ISOLATION LEVEL READ COMMITTED -- SET NOCOUNT ON SET NOCOUNT ON DECLARE @MaxWait int; SET @MaxWait = 60 IF EXISTS (SELECT 1 FROM [dbo].[Customers] WITH (READPAST) WHERE ([Status] = 1) AND (DATEDIFF(s, [LastUpdated], GETDATE()) > @MaxWait)) BEGIN SELECT 1 AS [IsWatchDogError] END ELSE BEGIN SELECT 0 AS [IsWatchDogError] END END Downloads The zip file below contains two SQL scripts: one to create a sample database with the above stored procedures and one to populate the sample database with 10,000 sample records.  I am very grateful to Red-Gate software for their excellent SQL Data Generator tool which enabled me to create these sample records in no time at all. References http://msdn.microsoft.com/en-us/library/ms187373.aspx http://www.techrepublic.com/article/using-nolock-and-readpast-table-hints-in-sql-server/6185492 http://geekswithblogs.net/gwiele/archive/2004/11/25/15974.aspx http://grounding.co.za/blogs/romiko/archive/2009/03/09/biztalk-sql-receive-location-deadlocks-dirty-reads-and-isolation-levels.aspx

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